Hi, I am working with the Q403 on testing power amps. My setup is a dummy load and Q403 and an oscilloscope connected to the amp’s output. Some amplifiers don’t like the input and output grounds connected and make oscillations and ground loops. I was considering making the connection of the 403 differential on the load and scope, but it enters noise into the system for some reason…
so my thinking is whether it is possible to modify my 403 to make the oscillator section floating from ground somehow? Or I need to build a special floating dummy load with buffered single-ended output for oscilloscope///
or even buing a 451 modifieng it to not block dc for my neads and attenuate 20 db instead of 12. with bigger power resistors…
Connect only the ground to the amplifier input, and measure the speaker output differentially…. Don’t connect ‘scope ground to the output either - that might be where the ground loop happened?
I have tried something similar to that, but one thing I haven’t tried is floating the ground on the amp’s input. I will make a test for that… Currently my setup does not allow floating load measurement because my load has a headfhone jack on the load (i use it to hear vaccum tubes microphonics and noise) I plan to build myself a customised load unit with floating loads, headphone amp with limiter with differintial input that enables me to hear the amp tested and split the signal to oscilloscope input and the Q403. It is a time-consuming project, but at the meantime, I try to solve it as is for my needs.